Sulfurized oil of improved color



States patent SUlLlFlJlRlZElD 01L OF IMPROVED COLOR STABILITY Harry E. Bloomshurg, Westtield, N. J., and Hugh T. dhearer, Jr., Pittsburgh, Pa, assignors to Ease Research and Engineering Company, a corporation of Delaware No Drawing. Application July 14, 1952, Serial No. 298,846

3 Claims. (Cl. 260-139) The present invention relates to sulfurized oils of improved color and color stability in storage, and relates also to a process for preparing such oils. More particularly it relates to a sulfurized mineral or fatty oil which is so processed as to prevent excessive darkening during and following the sulfurization process.

In the prior art numerous processes have been developed for sulfurizing various types of oils. The incorporation of sulfur into oil is frequently advantageous as in the case of the gear oil additives, metal working compositions such as cutting oils, and in many other products. The presence of sulfur increases the load carrying properties of lubricating oils and frequently has other advantages. Numerous processes and compositions have been developed in the prior art wherein substantial proportions of sulfur are incorporated into mineral base lubricating oils, animal oils such as lard oil, sperm oil, and the like, and even fatty oils of vegetable origin such as cottonseed oil, rapeseed oil, linseed oil, and others.

In general, sulfurization both of mineral oils and of fatty oils is accomplished by heating the oils with an efparticularly P453 and P235, are frequently employed and are satisfactory for the purposes of this invention. Other organic and inorganic sulfur compounds may be used but elemental sulfur and the phosphorus sulfides ordinarily are preferred.

A very serious disadvantage of prior art sulfurizing processes is the excessive darkening of the oil which occurs during the sulfurizing process, probably because of various types of oxidation processes which may take place. Sulfurized oils also have a strong tendency to darken further after the sulfurization process has been completed. When sulfurized fatty oils, for example, are used as additives in mineral oils, for instance, as extreme pressure lubricants, cutting oils, etc., an excessively dark color is commonly objectionable and this is particularly true in the case of metal working oils such as cutting and grinding oils. Lubricants of this character which are excessively dark and opaque tend to hide the work from the view of the machine operator, making it diflieult to carry out grinding, cutting, and other machining operations. A relatively light colored transparent oil is much preferred for such operations.

According to the present invention, the excessive darkening of oils due to sulfurization is substantially prevented by conducting the sulfurizing operations in the presence of a small amount of a salt of an appropriate type. In general, the salts should be alkali metal salts of weak acids, or mixtures of such salts, which give a basic reaction in aqueous solution, especially those having a pH value within the range of 9.5 to 11.2. Among such salts may be mentioned the carbonates of soda,

NazCOs, NaHCOa, and corresponding salts of the other alkali metals, also some of the borates, but especially the phosphates which contain at least two monovalent alkali metal atoms. The preferred material is trisodium phosphate, NasPOr. The disodium salt NazHPOi may also be used although it is somewhat less satisfactory. Proportions as small as 0.2% of the salt, based on the weight of the oil being sulfurized, are suficient to greatly reduce the darkening which is incidental to sulfurization.

Hence, mineral oils, especially mineral lubricating oils, may be sulfurized with elemental sulfur, or the phosphorus sulfides mentioned above, or with other sulfurizing agents, with or without an appropriate catalyst such as sulfurization or vulcanization promoters which are well known in the rubber industry, without excessive darkening in color or increase in opacity by simply incorporating into the oil a very small amount of trisodium phosphate or equivalent salt. This salt may be suspended in the oil in suitably sub-divided form, as for example by stirring a fine powder into the oil, or suspending a fabric or fibrous body impregnated with the salt in the body of oil being sulfurized.

The precise nature of the action by which darkening of the oil is prevented is not understood at this time. Apparently it has some relation to inhibition of oxidation of the oil but it does not impede the sulfuzrization of the oil appreciably. In view of the close similarity of sulfur and oxygen as regards their chemical activity with oils, it is interesting to note that these materials which apparently impede oxidation do not interfere with sulfurization.

In general, the process is applicable to oils in which substantial quantities of sulfur, for example, at least 1% and usually more, are to be incorporated. As usually manufactured, the oil is heated with elemental sulfur at an elevated temperature, commonly 350 F. or higher, with a resulting sulfurizing reaction which proceeds rather rapidly and causes rapid darkening of the oil in the absence of a preventive. Anhydrous trisodium phosphate, the preferred salt, is highly effective in small proportions but it is ordinarily desired to use about 1% of this salt, based on the Weight of the oil being treated. The invention will be more clearly understood with reference to the following examples and data.

EXAMPLE I A conventionally refined naphthenic lubricating oil, which may be referred to as mineral oil A, having a viscosity of about 40 S. S. U. at 210 F., was treated with elemental sulfur by stirring and heating in a steel vessel with paddle agitation at a temperature of 360 F. until the oil had picked up 1.10% by weight of sulfur in chemical combination. When this process was carried out in the absence of an agent to prevent darkening, the original color of the oil changed markedly, darkening from a rating of 1 /2 N. P. A. to 3 /2. This represents a Tag- Robinson color change of 17 /2 to 9. When the same process was repeated, adding 1% by weight of finely divided trisodium phosphate to the oil before heating or adding the sulfur, the sulfurized product with the same sulfur content, 1.10% darkened only very slightly, changing from 1 /2 to 2 on the N. P. A. scale or 17 /2 to 12% on the Tag-Robinson scale. The same product showed no appreciable sulfur separation when treated with trisodium phosphate wherein there was a measurable separation when the oil was sulfurized in the absence of the trisodium phosphate.

A similar experiment was repeated using a Mid-Continent, conventionally refined oil of the same viscosity,

40 S. S. U. at 210 E, which may be designated mineral Color improvement sulfurized mineral oils Composition, percent by wt. I II III -IV Mineral OilA pereeut 97.0 08.0 Mineral Oil B d Sulfur Na PO4 Colon-Original OilN. P. A ColorFinished Prod:

N P A EXAMPLE II Sperm oil having an original N. P. A. color of 2, Tag-Robinson 12%, was treated by heating 6 parts by weight of sulfur with'94 parts of oil to a temperature of 375 F. for a period of 1 /2 hours. All the sulfur combined with the oil. Here again, as inthe case of the mineral oil, the product was much darker and more opaque when there was no trisodium phosphate used in the process. The opaque character of the sulfurized sperm oil markedly affects the clarity and brilliance of blends in mineral oil. Consequently, the eliect on the user is much greater than can be shown by a recital of color test data. When 1% of trisodium phosphate was added the darkening was very much less as shown in Table IIA below.

EXAMPLE III Example 11 was repeated using lard oil of N. P. A. color 7, Tag-Robinson color 2, with very similar results which are tabulated in Table IIA.

TABLE IIA Fatty oils-6% sulfur 1 Eases prepared in the presence of trisodium phosphate were noticeably more transparent.

EXAMPLE IV Example It was repeated except that sulfurization was carried out with 12% sulfur. Twelve parts of sulfur were used with 88 parts of oil, by weight, the mixture being heated to a temperature of 375 F. for 1 /2 hours.

EXAMPLE V Example lll'was repeated except that the lard oil and sulfur were heated together until the product contained about 12% of'sulfur. These'results are shown in Table 1113.

TABLE IIB Fatty oils-'12 sulfur Composition, percent by wt. IX XI XII Sperm Oil (N. P. A. Color 2, Tag- Robinson 12%).

Lard Oil (N. I. A. Color 7, Tag- Robinson 2).

Black.

The'bases containing trisodium phosphate were noticeably more transparent.

"In both Examples IV and V the use of 1% of trisodium phosphate, based on the weight of "the oil, produced a product which was transparent although all of them were fairly black in appearance by reflected light. It should be noted that sulfurized sperm oil and sulfurized lard oil are seldom used straight but they are usually blended in mineral oils in small proportions (1% to 15%) to impart oiliness and load carrying properties as in gear oils, cutting oils, grinding oils and the like.

Accordingly, blends were prepared in mineral oil using 5% of the products which contained 6% sulfur and 2 /z% by weight'of the products which contained 12% sulfur, both being incorporated in oils of type B mentioned above. The results of color tests on theseblends are summarized in Tables IIIA and IIIB.

TABLE 111A 5 wt. percent blends of 6% sulfurized fatty oils of Table 'IIA vin mineral oil B 1 15% of the above 5% blend diluted with (by volume) of water white kerosene.

TABLE IIIB 2 /2 wt. percent blends of 12% sulfurizea' fatty oils of Table HR in mineral oil B Sulfurized Fatty Oil Composition IX X XI XII Color:

N. P. A 5% 8 6 6 Tag-Robinson '3 1 2% 2% Dilute Color N. P. A 2 3% 2% 2% Tag-Robinson 12% 9 11 11 1 See Table IIIA above.

It should be noted that an appreciable reduction in opacity of a blending agent, such as sulfurized fatty oils, used in cutting oils makes a very appreciable improve ment in the utility of such oils for fine machine work. Products made according to the process of this invention, therefore,'have a premium value in the cutting and grinding oil field. It will be understood that various other ingredients may be added to the oils either before orafter processing and that the invention is applicable to other oils and sulfurizing processes besides those specifically enumerated above.

What is claimedis:

1. The process of sulfurizing an oil selected from the group consisting of mineral and fatty oils to obtain a product of relatively light stable color and high stable transparency which comprises heating said .oil to a temperature of at least300 F. with 5 to 40% by weight, based on the oil, of a sulfurizing agent selected from the group consisting of elemental sulfur and phosphorus sulfides, in the presence of at least 0.2% based on the weight of said oil, of trisodium phosphate.

2. Process according to claim 1 wherein the oil is a mineral base oil of lubricating viscosity range.

'3. Process according to claim 1 wherein the oil is an animal fatty oil.

References Cited in the file of this patent UNITED STATES PATENTS 1,869,557 Gillespie Aug. .2, 1932 1,926,687 Palmeriet'al Sept. 12,1933 2,538,941 Macallum Jan. 23, 1951 2,592,624 Veatch et-al Apr. 15, 1952 2,644,810 ,Beretvas July 7,1953 2,690,445 :Corcoran et,al., Sept. 28, 1954 

1. THE PROCESS OF SULFURIZING AN OIL SELECTED FROM THE GROUP CONSISTING OF MINERAL AND FATTY OILS TO OBTAIN A PRODUCT OF RELATIVELY LIGHT STABLE COLOR AND HIGH STABLE TRANSPARENCY WHICH COMPRISES HEATING SAID OIL TO A TEMPERATURE OF AT LEAST 300* F. WITH 5 TO 40% BY WEIGHT, BASED ON THE OIL, OF A SULFURIZING AGENT SELECTED FROM THE GROUP CONSISTING OF ELEMENTAL SULFUR AND PHOSPHORUS SULFIDES, IN THE PRESENCE OF AT LEAST 0.2% BASED ON THE WEIGHT OF SAID OIL, OF TRISODIUM PHOSPHATE. 